Re: [PATCH v2 bpf-next 2/2] selftests/bpf: Add tests for BPF_NEG range tracking logic

[Eduard Zingerman <eddyz87@gmail.com>]

On Tue, 2025-06-24 at 22:49 +0000, Song Liu wrote:
> 
> > On Jun 24, 2025, at 3:18 PM, Eduard Zingerman <eddyz87@gmail.com> wrote:
> > 
> > On Tue, 2025-06-24 at 15:00 -0700, Song Liu wrote:
> > 
> > [...]
> > 
> > > +SEC("lsm.s/socket_connect")
> > > +__success __log_level(2)
> > > +__msg("0: (b7) r0 = 1")
> > > +__msg("1: (84) w0 = -w0")
> > 
> > Sorry, my previous comment probably was ambiguous.
> > What I meant is that you can match verifier output for "w0 = -w0 ; R0=-1",
> > thus checking that inferred value for "w0".
> 
> Ah, I removed that part because I found some other __msg doesn’t have
> the whole line. Let me add it back. 

Note: if you need to shorten the matched line you can use regexs
      inside __msg strings: __msg("... {{regex-here}} ...")

> Thanks,
> Song
> 
> > 
> > > +__msg("mark_precise: frame0: last_idx 2 first_idx 0 subseq_idx -1")
> > > +__msg("mark_precise: frame0: regs=r0 stack= before 1: (84) w0 = -w0")
> > > +__msg("mark_precise: frame0: regs=r0 stack= before 0: (b7) r0 = 1")
> > > +__naked int bpf_neg_2(void)
> > > +{
> > > + /*
> > > + * lsm.s/socket_connect requires a return value within [-4095, 0].
> > > + * Returning -1 is allowed
> > > + */
> > > + asm volatile (
> > > + "r0 = 1;"
> > > + "w0 = -w0;"
> > > + "exit;"
> > > + ::: __clobber_all);
> > > +}
> > 
> > [...]